Objective A recent randomized controlled trial suggested that early gestational diabetes mellitus (GDM) screening in patients with obesity (body mass index [BMI] >= 30 kg/m(2) ) does not improve perinatal outcomes. The American College of Obstetrics and Gynecology currently recommends early screening for gestational diabetes in patients who are overweight with one or more additional risk factors. We evaluated the effect of screening based on the number of additional risk factors for development of gestational diabetes.Study Design This was a secondary analysis of a multicenter randomized controlled trial of obese patients with singleton nonanomalous fetuses comparing early (14-20 weeks' gestation) with routine (24-28 weeks' gestation) GDM screening. Exclusion criteria were pregestational diabetes, major medical illnesses, bariatric surgery, chronic steroid use, and prior cesarean. Early versus routine GDM screening groups were compared and stratified by the number of additional risk factors for GDM (0, 1, 2, and >= 3). The primary outcome was an adverse perinatal composite outcome composed of: macrosomia, primary cesarean delivery, hypertensive disorders of pregnancy, shoulder dystocia, neonatal hyperbilirubinemia, and neonatal hypoglycemia. Analyses examined effects of early versus routine screening by the number of additional risk factors and their possible interaction on the incidences of the primary outcome and GDM.Results Of 913 patients, 5% had 0, 52% had 1, 33% had 2, and 10% had >= 3 additional risk factors. Baseline characteristics, including the number and type of risk factors, were similar between early and routine screening groups. Breslow-Day test for interaction between early versus routine screening and the number of additional risk factors was not significant for either the primary outcome ( p = 0.37) or the diagnosis of GDM ( p = 0.28). The incidence of GDM and the adverse perinatal composite outcome increased as the number of risk factors increased ( p < 0.001).Conclusion In patients with BMI >= 30 kg/m(2) and additional risk factors, early GDM screening does not prevent adverse outcomes.